Clip for surface treating tool



Dec. 15, 1970 A. A. HUTCHINS CLIP FOR SURFACE TREATING TOOL Filed Nov. 29, 1968 E .1 q6 E 1 q-? INVENTOR. H 4 A? Hu T'CH/MS TTOQJEV United States Patent Ofi ice 3,546,822 Patented Dec. 15, 1970 3,546,822 CLIP FOR SURFACE TREATING TOOL Alma A. Hutchins, 49 N. Lotus Ave., Pasadena, Calif. 91107 Filed Nov. 29, 1968, Ser. No. 780,145 Int. Cl. B24b 23/00 US. Cl. 51-170 16 Claims ABSTRACT OF THE DISCLOSURE A clip for securing a sheet of sandpaper On a powered sanding machine, and including a shoulder structure pr jecting upwardly at the upper side of a sandpaper carrying shoe of the machine, and toward which a pivotal clip element is spring urged downwardly, in a relation such that the end portion of the sheet of sandpaper extends first generally horizontally at the upper side of the shoe, then upwardly between two generally vertical surfaces of the shoulder structure and clip element, and then generally horizontally between an upper portion of the clip element and an upper surface of the shoulder structure, all in a relation tightly and positively clamping the sandpaper sheet in place. The clip element is mounted for its pivotal movement by a pin which passes through apertures in a mounting bracket and in the clip element respectively, and which has a groove partially receiving portions of the mounting bracket and clip element in a manner releasably retaining the pin against axial separation from the other parts.

BACKGROUND OF THE INVENTION This invention relates to improved clip units for releasably but positively securing a sheet of sandpaper or other surface treating material to the oscillatory head of a power driven sanding machine or the like.

Under the vibratory conditions which are encountered in portable power driven sanding machines or other surface treating machines, it is extremely difiicult to secure the sandpaper or other surface treating sheet of material in position on the oscillatory shoe of the tool as effectively as would be desired for an optimum surface treating operation. Though numerous different types of retaining clips have been designed for this purpose in the past, most of them have retained the sheet material only very inetfectively, and in a manner enabling gradual and slight shifting movement of the retained ends of the sandpaper or other sheet material out of their tightly retained engagement with the holding clips, under the vibrational conditions encountered in use, with the result that the paper may relatively rapidly detach itself from the clips, or may loosen just sufiiciently to enable rapid tearing of the sheet by the intermittently changing forces applied to it when the machine is under power.

Most power sander clips have also had the further disadvantage of being more difficult to assemble, and to disassemble for replacement, than would be desired. With regard particularly to the pivot pins employed in constructing conventional clip units, these pins have in the past been so constructed as to necessitate upsetting or peening over of their opposite ends in order to complete the pivotal connection, and in a manner rendering disassembly of the clip unit for repair or replacement extremely difiicult if not impossible from a practical standpoint.

the sandpaper or other work engaging surface treating sheet material are retained so positively and effectively in fixed positions relative to the oscillatory shoe of the machine as to positively preclude any possibility whatever of even the slightest shifting movement of the retained ends of the sheet material, so that the sheet material is held in a very tight condition adjacent the underside of the s and cannot shift even slightly relative to that shoe in operation. Thus, the sheet material is assured of a maximum useful life, with no tearing as a result of the usual slight shifting movement of the sandpaper relative to the shoe, and with no danger of dislocation of the sheet material from the shoe until an operator purposely detaches the paper for replacement after extended operational use.

To achieve this positive retention of the sheet material, I employ a clip device, which is mounted to the upper side of the oscillatory shoe, and which includes a shoulder structure carried by the shoe, and a movable clip unit mounted for pivotal movement upwardly and downward- 1y relative to the shoulder structure, and between an upper open position and a lower position in clamping relation with respect to the shoulder structure. The shoulder structure has an upwardly extending first surface, and a top surface at the upper edge of the first surface, with the pivotal clip unit having a downwardly projecting first portion to be received opposite the mentioned first surface of the shoulder structure, and a generally horizontal upper portion to extend across the upper side of the top surface of the shoulder structure. Thus, when the clip element is in its holding position, the end of the sandpaper or other sheet material extends first generally horizontally, then generally vertically between the two first portions of the shoulder structure and clip unit, and then generally horizontally between the upper surface of the shoulder structure and the top portion of the pivotal clip unit, all in a manner attaining the desired positive and unyielding retention of the sheet material. The relationship between the movable and stationary parts is preferably such that the spring urged pivotal movement of the clip unit is in a direction attaining an effective gripping or clamping action against both the vertical and horizontal portions of the sheet material. Also, the clamping action is maximized by providing the pivotal clip unit with a resiliently deformable gripping element for actually contacting the sheet material.

With regard to the mentioned pivot pin for mounting the clip unit for its pivotal clamping action, this pin is desirably so constructed as to have a unique interfitting relationship with the pivotal element and its mounting bracket, which relationship enables much more rapid assembly and disassembly of the parts than has been possible in prior devices of this general type. More particularly, this is attained by providing the pin with a shoulder or shoulders movable into the desired interfitting relation with respect to the engaged parts by shifting movement of the pin first longitudinally and then transversely of its axis. For best results, the pin has an annular groove within which portions of the pivotal element and its mounting bracket are received, in spring retained relation, during normal operation of the device, but from which those elements are removable by slight transverse shifting movement of the pin.

BRIEF DESCRIPTION OF THE DRAWING The above and other features and objects of the invention will be better understood from the following detailed description of the typical embodiment illustrated in the accompanying drawing in which:

FIG. 1 is a side view of a sanding machine, or other surface treating machine, having clips constructed in accordance with the invention;

FIG. 2 is an enlarged fragmentary perspective view of olne end of the FIG. 1 machine, and one of its retaining c rps;

FIG. 3 is an exploded perspective representation of the clip;

FIG. 4 is a fragmentary enlarged s1de view of one of the clips;

FIG. 5 is an enlarged fragmentary vertical section taken on line 55 of FIG. 4; and

FIGS. 6, 7 and 8 are fragmentary vertical sections taken on lines 6-6, 77 and 88 respectively of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, I have shown at 10 a power driven surface treating machine, having a main body portion 11 with handles 12 and 13 by which an operator manipulates the machine to sand or otherwise treat a typically horizontal work surface 14. An oscillatory shoe 15 carries a conventional sheet of sandpaper or other surface treating sheet material 16 at its underside for engaging and acting on work surface 14. Body 11 of the machine contains a power driven motor 17, having a shaft which turns about a vertical axis 18, with the shaft typically having an eccentric portion 19 rotatably received within a bearing structure 20 projecting upwardly from the upperside of shoe 15, in a manner giving to the shoe an orbital type motion, in a manner well understood in the art. Rubber cushions 21 connect body 11 to shoe 15 to prevent rotation of the shoe relative to the body, and thus confine the shoe for its desired limited orbital motion. The opposite ends of the sandpaper 16 are detachably secured to the shoe by a pair of clip devices 22, constructed in accordance with the present invention.

Shoe 15 may include a rigid shoe body 23, typically formed of sheet aluminum or other rigid sheet metal or the like, with this body having a main horizontal portion 24 which is rectangular in horizontal section, and which carries two upwardly projecting parallel opposite side flanges 25 for giving to the body the desired rigidity. At its underside, shoe body 24 may carry a cushion 26, also of rectangular horizontal section, and typically very slightly larger horizontally than is the shoe body 24. Cushion 26 has an upper horizontal planar surface 27 suitably cemented or otherwise tightly bonded or secured to the undersurface of shoe body 24. This cushion 26 may for example be formed of foam rubber or any other suitable cushioning substance. The undersurface 28 of cushion 26 is planar and parallel to portion 24 of the shoe body 23, and in the FIG. 1 position of the tool extends horizontally above and parallel to work surface 14.

The sandpaper or other work engaging sheet material 16 takes the form of an elongated rectangular strip of such material, having a main portion 29 (FIG. 1) which extends along the undersurface of cushion 26. At its opposite ends, the strip of sandpaper extends upwardly at 30, and then generally horizontally inwardly at 31 to engage and to be retained by the two clip devices 22.

To now describe the structure of the clip devices per se, each of these devices 22 includes a mounting bracket 32 and a pivotally movable clip unit 33, mounted to swing upwardly and downwardly about a pivot pin 34 relative to mounting bracket 32, and between the broken line position of FIG. 4 and the full line position of that figure. The mounting bracket 32 is formed of rigid sheet metal or another suitable rigid substance, desirably having a horizontal main portion 35 (FIG. 4) which extends along the upper surface of portion 24 of the shoe body 23, and is secured thereto by screws 36 and coacting nuts 37. Along its rear edge, mounting bracket 32 has an upturned vertical flange 38. At its forward edge, the sheet metal bracket element 32 has a second and similar upturned vertical flange 39, lying in a preferably directly vertical plane, and having a horizontal top edge 40, disposed parallel to the plane of the undersurface 28 of the shoe. Between these two flanges 38 and 39, the sheet material of bracket 32 has two upwardly deflected portions 41 and 42 forming spaced parallel vertical mounting arms to which pivot pin 34 is connected. These arms 41 and 42 contain circular apertures 43, of a common diameter, and aligned with one another along a horizontal axis 44 disposed parallel to edge 40 of flange 39, and parallel to undersurface 28 of the shoe.

The pivotal clip unit 33 includes a main rigid part 46 formed of essentially rigid sheet metal or the like, and a resiliently deformable elastomeric cushion element 47 of rubber or the like. Part 46 has a main planar portion 48, which at 49 is of a relatively extended length parallel to axis 44 (a length desirably equaling that of upturned flange 39 of bracket 32), and at 50 is of a reduced length and forms two downturned parallel mounting arms 51 containing aligned circular apertures 52 of a diameter corresponding to that of apertures 43 of the arms 41 and 42. As seen best in FIG. 5, the axial spacing of the two arms 51 of part 46 may be slightly greater than the axial spacing of the two coacting arms 41 and 42 of part 32.

Pin 34 has an outer cylindrical surface 53 extending along most of its length, and of a diameter corresponding to or very slightly less than the diameter of apertures 43 and 52 in mounting arms 41, 42 and 51. At one end of this surface 53, the pin contains an annular groove 54, whose cylindrical reduced diameter surface 54 is concentric with surface 53, and which groove is defined at its opposite axial ends by two parallel annular surfaces 55 disposed directly transversely of the axis 56 of the pin. Beyond the groove, the pin may have a short head portion presenting an outer cylindrical surface 57 of a diameter corresponding to, and axially aligned with, the previously mentioned extended axial surface 53 of the pin. The opposite end of the pin may be tapered slightly at 58, to facilitate insertion of the pin into apertures 43 and 52 and to the assembled position of FIG. 5, in which the pin mounts pivotal unit 33 for its upward and downward swinging movement relative to the mounting bracket 32.

Disposed about pin 34, at a location axially intermediate the two upstanding mountaing arms 41 and 42 of bracket 32, there is provided a coil spring 59, which may have an internal diameter very slightly larger than the external diameter of the main portion of the pin, and which spring has a first end 60 (FIG. 7) bearing downwardly against flange 38 of the mounting bracket 32, and a second end 61 extending through an aperture 62 in part 46, with end 61 having a turned portion 63 hearing downwardly against the upper surface of part 46 to yieldingly urge part 46 downwardly to its FIG. 4 position. A portion 64 of part 46 is turned angularly as seen in FIG. 4 and the other figures, to form a handle by which the part 46 may be manually swung upwardly against the tendency of spring 59, to receive the end of the sandpaper sheet 29. i

As seen clearly in FIGS. 5, 7 and 8, the downward forces exerted by portions 60 and 63 of the spring against flange 38 and part 46 respectively are counteracted by an upward force exerted by the coiled portion of the spring against the underside of pin 34, in a manner yieldingly urging the pin upwardly (transversely of its axis 56) and relative to both of the parts 32 and 46, so that the grooved portion 54 of the pin is not centered within its coacting apertures 43 and 52, but rather is urged upwardly to an eccentric position with respect to those apertures, and therefore so that the arms 42 and 51 project into the groove at 65 (FIG. 5). Thus the vertical planar opposite side surfaces of the sheet metal forming these arms are engageable with the transverse vertical planar shoulders 55 defining opposite ends of the groove, to eifectively retain the pin against axial displacement in either direction relative to the apertured parts. In this way, the spring 59 holds the pin in such a relation with respect to the pivotally connected parts as to maintain these parts and the pin in their proper assembled relation, and against axial separating movement, unless and until the pin is forcibly moved downwardly at the location of groove 54 and into coaxial alignment with apertures 43 and 52, to enable axial movement of the pin from its assembled position.

At its forward edge, horizontal portion 48 of swinging part 46 is turned downwardly to form a downturned flange or edge portion 66, terminating at a horizontal edge 67. In the FIG. 4 clamping position, this flange 66 extends approximately parallel to the vertical upturned flange 39 of mounting bracket 32, and is opposite that flange. Mounted to the underside of part 46, there is provided a previously mentioned cushion element 47, desirably formed of an'appropriate rubber or other resiliently deformable elastomeric material. This cushion has a downwardly projecting portion 68 received inwardly of and lining the downwardly projecting flange 66 of part 46, and has a generally horizontal but somewhat inclined upper portion 69 which is essentially planar and engages upwardly against the undersurface of the planar portion 48 of part 46. At its underside, portion 69 of cushion 47 has a desirably planar surface 70, disposed parallel to the upper surface 71 of the same part, and adapted to engage downwardly against the end of the sandpaper. A pair of upwardly extending elastomeric projections 72 molded integrally with cushion 47 project upwardly through apertures 73 in part 46, and are tight frictional fits within those apertures in a manner effectively securing the cushion in the FIG. 4 position of assembly with respect to part 46, and connecting cushion 47 for upward and downward swinging movement with part 46. Cushion 47, and its planar surface 70, and its downward projecting portion 68, with its generally vertical surface 74, all desirably extend through a length corresponding approximately to the length of upturned flange 39 of part 32.

To now describe the manner of use of the illustrated clip device 22, a sheet of sandpaper is attached to the tool by first extending the main portion of the sandpaper along the underside of shoe 15, and then turning the opposite end of the sandpaper upwardly at 30 and then inwardly at 31. Each of the pivotal clip elements 33 is swung upwardly against the tendency of its spring 59 and to the position of the left hand clip in FIG. 1, so that the end of the sandpaper may be inserted beneath unit 33, following which the latter is allowed to swing downwardly under the influence of its spring 59 to the FIG. 4 clamping position, in which the end of the sandpaper is clamped tightly and effectively between cushion 47 and the upturned flange or shoulder structure 39. In this FIG. 4 position, the end of the paper first extends generally horizontally at 31, then extends upwardly between portion 68 of cushion 47 and the outer or forward vertically extending surface 39' of flange 39, following which the upper extremity of the sandpaper ultimately turns generally horizontally again at 75 between the upper edge 40 of flange 39 and the undersurface of the top generally horizontal portion of cushion 47. In the FIG. 4 holding position, spring 59 is still deformed sufliciently to exert a very substantial downward force on part 46, to tightly clamp the end of the sandpaper in position. It is also noted that this force is such as to urge portion 68 continuously toward flange 39, and to simultaneously urge surface 70 of the cushion continuously downwardly toward upper edge 40 of flange 39, so that both the vertical and horizontal portions of the sandpaper are tightly and continuously and simultaneously clamped between the cushion and flange 39. This is true in part because the tangential force exerted by cushion 47 about its pivotal axis in the FIG. 4 position, which tangential force is represented diagrammatically at 76 in FIG. 4, has a first component 77 in a direction inwardly toward surface 39' of flange 39, and a second component 78 downwardly against the upper edge 40 of flange 3-9. Stated differently, it is noted that surfaces 39' and 40 of flange 39 are so oriented that neither extends directly tangentially with respect to a circle 39" drawn through or adjacent to these surfaces about the pivotal axis of part 46. Further, as seen in FIG. 4, it

is desirable for best clamping action that portion 63 of spring 59 engage and act against element 33 at a location at least about as far from axis 44 as is the upper surface 40 of flange 39, and preferably at substantially the same distance from that axis as is surface 40 to thereby bear against element 33 at substantially the diameter of circle 39 of FIG. 4, in a manner maximizing the effectiveness with which elements 33 and 47 clamp the sandpaper against flange 39.

In assembling the clip structure, the pin 34 is merely inserted axially into apertures 43 and 52 until it reaches the FIG. 5 position, at which the groove 54 automatically locks the pin in that setting. To remove the pin the latter is pressed downwardly a slight distance at the location of the groove, until the pin is coaxial with apertures 43 and 52 at the groove, and is then easily separated axially from the connected parts.

I claim:

1. In a sanding machine or the like, the combination comprising a shoe adapted to extend horizontally above and be power oscillated relative to a work surface, said shoe having an undersurface along which a sheet of surface treating material is to extend for engaging and actrng on said work surface, with an end of said sheet extending upwardly at an end of said shoe and then extending generally horizontally inwardly along the upper side of the shoe, means forming a retaining shoulder structure carried at the upper side of the shoe and having an upwardly extending first surface facing generally toward said end of the shoe and an upwardly facing top surface at the upper edge of said first surface, a clip unit mounted pivotally to the upper side of said shoe to swing generally upwardly and downwardly relative to said shoulder structure between an upper open position and a lower holding position in clamping relation with the shoulder structure, and a spring yieldingly urging said clip unit downwardly to said holding position, said clip unit having a downwardly projecting portion which in said holding position extends downwardly opposite said first surface of said shoulder structure in a relation confining a generally vertical portion of said sheet therebetween, and said clip unit having an upper generally horizontal portion which in said holding position extends generally horizontally across and above said top surface of said shoulder structure in a relation confining a generally horizontal portion of the sheet therebetween, whereby said end of the sheet when retained extends first generally horizontally toward said first surface, then generally upwardly between said upwardly extending first surface and said downwardly projecting portion of the clip unit, and then generally horizontally between said top surface of the shoulder structure and said upper portion of the clip unit.

2. The combination as recited in claim 1, in which said clip unit includes an essentially rigid body mounted for said upward and downward swinging movement, a resiliently deformable cushioning element for resiliently clamping said sheet against the shoulder structure, said cushioning element forming said downwardly projecting portion and said upper generally horizontal portion of the clip unit.

3. The combination as recited in claim 1, in which said clip unit includes an essentially rigid body mounted for said upward and downward swinging movement, and a resiliently deformable cushioning element for resiliently clamping said sheet against the shoulder structure, said cushioning element forming said downwardly projecting portion and said upper generally horizontal portion of the clip unit, and said body having essentially rigid downwardly projecting and upper portions received adjacent and backing up the corresponding portions of the cushioning element.

4. The combination as recited in claim 1, in which said clip unit includes an essentially rigid body mounted for said upward and downward swinging movement, and a resiliently deformable cushioning element for resilient- 1y clamping said sheet against the shoulder structure, said cushioning element forming said downwardly projecting portion and said upper generally horizontal portion of the clip unit, said cushioning element having a plurality of projections extending through apertures in said body and retained therein to secure the cushioning element to the body.

5. The combination as recited in claim 1, in which said clip unit includes an essentially rigid body mounted for said upward and downward swinging movement, and a resiliently deformable cushioning element for resiliently clamping said sheet against the shoulder structure, said cushioning element forming said downwardly projecting portion and said upper generally horizontal portion of the clip unit, and said body having essentially rigid downwardly projecting and upper portions received adjacent and backing up the corresponding portions of the cushioning element, said upper portion of the cushioning element having a plurality of projections extending upwardly through and frictionally retained within apertures in M said upper portion of said body.

6. The combination as recited in claim 5, including an essentially rigid bracket secured to the upper side of said shoe and mounting said clip unit for said swinging movement, said bracket having an upturned edge forming said shoulder structure.

'7. The combination as recited in claim 6, in which the pivotal axis of said clip unit is so located relative to said shoulder structure that downward clamping force exerted by said clip unit against said sheet has a first component acting inwardly toward said upwardly extending first surface of the clip structure to clamp the sheet thereagainst, and has a second component acting downwardly toward said top surface of the shoulder structure to also clamp the sheet thereagainst.

8. The combination as recited in claim 1, including an essentially rigid bracket secured to the upper side of side shoe and mounting said clip unit for said swinging movement, said bracket having an upturned edge forming said shoulder structure.

9. The combination as recited in claim 1, in which the pivotal axis of said clip unit is so located relative to said shoulder structure that downward clamping force exerted by said clip unit against said sheet has a first component acting inwardly toward said upwardly extending first surface of the clip structure to clamp the sheet thereagainst, and has a second component acting downwardly toward said top surface of the shoulder structure to also clamp the sheet thereagainst.

10. In a sanding machine, a device for retaining an end of a sheet of surface treating material and including a mounting bracket section containing at least one aperture, a swinging clip section for retaining the sheet and containing at least one aperture, and a pivot pin extending through said apertures of said sections to mount said clip section for pivotal movement relative to said bracket section, said pin having a shoulder which in a predetermined assembled position bears against one of said sections adjacent one of said apertures in a relation locking the pin against removal from that aperture, but which is small enough to pass through said aperture and break the pivotal connection upon predetermined slight shifting movement of the pin transversely of its axis.

11. The apparatus as recited in claim 10, including means yieldingly urging said pin transversely to said assembled position to maintain said pivotal connection.

12. The apparatus as recited in claim 10, including means yieldingly urging said clip section pivotally relative to said bracket section and also yieldingly urging said pin transversely to said assembled position thereof.

13. The apparatus as recited in claim 10, including a coil spring disposed about said pin and having ends bearing against said bracket section and said clip section in a relation urging the latter pivotally, and bearing against said pin in a relation urging it transversely to said assembled position thereof.

14. The apparatus as recited in claim 13, in which said pin contains a reduced diameter groove receiving portions of said bracket section and said clip section at said apertures to retain said pin against axial movement relative to both of the sections.

15. The apparatus as recited in claim 13, in which said bracket section has two arms containing two of said apertures, and said clip section also has two arms containing two apertures, said pin containing an annular groove receiving portions of two corresponding arms of said bracket section and said clip section.

16. The apparatus as recited in claim 10, in which said pin contains a groove receiving portions of said bracket section and said clip section at said apertures in a relation retaining said pin against relative axial movement.

References Cited UNITED STATES PATENTS WILLIAM R. ARMSTRONG, Primary Examiner US. Cl. X.R. 

